Stable isotope analyses reveal individual variability in the trophic ecology of a top marine predator, the southern elephant seal

Identifying individuals' foraging strategies is critical to understanding the ecology of a species, and can provide the means to predict possible ecological responses to environmental change. Our study combines stable isotope analysis and satellite telemetry to study the variability in individual foraging strategies of adult female southern elephant seals (). Our hypothesis is that female elephant seals from the Western Antarctica Peninsula (WAP) display individual specialization in their diets. We captured adult female elephant seals ( = 56, 2005-2009) at Livingston Island (Antarctica), and instrumented them with SMRU-CTD satellite tags. We collected blood, fur, and vibrissae samples for delta C-13 and delta N-15 analyses. The mean values for all vibrissae were -21.0 +/- A 0.7aEuro degrees for delta C-13, and 10.4 +/- A 0.8aEuro degrees, for delta N-15. The individual variability of delta C-13 (60%) was more important than the within-individual variability (40%) in explaining the total variance observed in our data. For delta N-15, the results showed the opposite trend, with the within-individual variability (64%) contributing more to the total variance than the individual variability (36%), likely associated with the effect that the fasting periods have on delta N-15 values. Most individuals were specialists, as inferred from the low intra-individual variability of delta C-13 values with respect to the population variability, with half the individuals utilizing 31% or less of their available niche. We found eight different foraging strategies for these animals. Female elephant seals from the WAP are a diverse group of predators with individuals utilizing only a small portion of the total available niche, with the consequent potential to expand their foraging habits to exploit other resources or environments in the Southern Ocean.